package com.singzi.leetcode.niuke;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n  = in.nextInt();
        int []nums = new int[n];
        for (int i = 0; i < n; i++) {
            int temp  = in.nextInt();
            nums[i] = temp;
        }
        for (int i = 0; i < n; i++) {
            if(i%3 == 0) System.out.print(nums[i]);
        }
    }
}
